Forsmark 1 turbines to get new blades

New blades are to be installed in the low-pressure turbines at unit 1 of Sweden's Forsmark nuclear power plant during an upcoming maintenance outage. The new blades are designed to reduce vibrations, which have affected the current blades.

New blades are to be installed in the low-pressure turbines at unit 1 of Sweden's Forsmark nuclear power plant during an upcoming maintenance outage. The new blades are designed to reduce vibrations, which have affected the current blades.

A turbine blade undergoes inspection (Image: Vattenfall)

A maintenance shutdown is scheduled to take place at Forsmark 1 between 3 May and 11 June. During this period, the blades in the two turbines at the unit will be replaced in order to resolve a problem with vibration that has affected the existing blades in the turbines' 'drain' section - the final section that steam passes through before it is sent to the unit's condenser. Both turbines at Forsmark 1 have a total of 612 blades within this section.

The low-pressure turbines at the unit were installed in 2005. However, during subsequent inspections abrasion damage on the tips of these blades was discovered. Vibration of the blades was believed to be the cause. The turbine rotor spins at 3000 rpm, driving the generator. However, measurements showed the blades began to vibrate when the rotor speed was about 2500 rpm. This vibration occurred because the turbine blades' own frequency is similar.

Project leader Andreas Björck said, "The new blades being fitted are designed so they have different natural frequencies, which reduces vibrations. During the startup of Forsmark 1 measurements will be repeated to check that the blades do not vibrate."

During the audit, the 708 secondary blades, sitting in front of the 'drain' blades, will undergo magnetic particle tests to check for cracks.

Researched and written
by World Nuclear News